1. Field of the Invention
The present invention relates to a power wheelchair having a touchpad which is used by the person seated therein, e.g. by a single finger or other slight pressure, to control the speed and direction of the wheelchair.
2. Background Art
It is well known that physically handicapped individuals with such disabilities as spinal cord injury, muscular dystrophy, multiple sclerosis, cerebral palsy or arthritis need the assistance of a power wheelchair to be mobile. Heretofore, wheelchairs may be difficult for some users to control if they have severely limited hand and/or finger range and strength.
U.S. Pat. No. 5,778,996 teaches a combination power wheelchair and power walker providing dual controls that may be used by either a seated user or a user walking behind and partially supported by the mobility aid. A hand control assembly provides a seated user with an on-off switch and forward-off-reverse switches for each motor. A direction controller assembly connects and provides coordinated movement of the left and right switch handles of the hand control assembly. The direction controller assembly allows the user to operate both switches with one hand by means of pushing, pulling or twisting motions, and replaces an expensive joystick assembly. A walker control assembly which overrides the hand control assembly, allows a walking user to operate both motors in either a forward or reverse direction, and to easily control walker speed and direction with gentle pushes or pulls on the walker handles. The left and right motors drive rear wheels through a shock absorbing flex coupling that tends to absorb the initial jolt when either motor is turned on.
U.S. Pat. No. 5,542,690 teaches a wheelchair for controlled environments including a pair of tubular sideframes interconnected by a seat and a backrest. Sockets are welded to the sideframes for receiving pins on the underside of the seat. The position of the backrest is adjustable and the backrest is separated from the seat by a gap to avoid trapping contaminants. All metal components of the wheelchair have in integral outer surface. Tacky rollers clean the wheels as the wheelchair rolls and mechanically couple a power unit to the rear wheels. The power unit is controlled from a keyboard attached to a tubular armrest on the wheelchair. Control and signal cables from the keyboard are located within the armrest. A protective garment is provided with the wheelchair to contain contaminants in the clothing of the user and to protect the user.
U.S. Pat. No. 4,493,219 teaches an energy conversion and transmission device is disclosed which, in its preferred embodiment, has a rigid substrate with a resistive area printed on its top surface, a spacer of non-conductive material with an aperture therethrough positioned in register with the rigid substrate resistive area, and a flexible substrate with a resistive area printed on its bottom surface in register with the aperture and the rigid substrate resistive area so that application of a force to the flexible substrate with an elastomeric actuator will move the flexible substrate resistive area to establish an electrical contact area with the rigid substrate resistive area, which electrical contact area increases and, thus, the resistivity of that area decreases as the applied force increases. Thus, when an electrical potential is applied across the two resistive areas, current flow through the two resistive areas increases as the applied force increases. Capacitive, inductive and other embodiments of the device are also disclosed.
U.S. Pat. No. 5,648,708 teaches an apparatus and method that allows a user to exert a force to control a motive machine. The exerted force is transferred by a force transferring means to force sensors which detect the amount and direction in which the force is exerted. The force sensors convert the applied force into an electrical signal, which is used to control the motive features of a machine.
U.S. Pat. No. 4,444,998 teaches a touch controlled membrane device producing an output signal which is a function of any dual coordinate location resulting from an applied pressure in a two dimensional resistive field. In one preferred embodiment, a single resistive film is spaced from a coextensive conductive film. First and second source voltages are alternately applied across orthogonal axis directions of the resistive film to establish voltage gradients in both directions. Pressure applied to the conductive film brings the conductive and resistive films into contact so that a unique two-component output signal appears on the conductive film, which defines the X, and Y coordinates of the location of the applied pressure. In a second embodiment, two resistive films are mounted opposite to two conductive surfaces applied onto opposite sides of an insulative film, and voltage is applied to the resistive films in orthogonally related directions. Pressure applied to one resistive film causes both resistive films to contact the conductive surfaces so that the voltages applied to each conductive surface represent the coordinates of the point of contact.